Spinnable carboxymethylated cotton fibers and their production



Patented Dec. 22, 1953 SPINN'ABLE CARBOXYMETHYLATED GOT- 4 TON FIBERSTHEIR PRODUCTION George 0. Daul, John 1 Reid, and Robert M. Reinhardt,New Orleans", La., assignors to the United States of America asrepresented by the Secretary of Agriculture N Drawing. Application July10, 1951,

- serialism-236,051

.2 Claims. (01. 8-129) mn dund r The invention herein describedmay bemanufactured and usedby or for the Government of the United States ofAmerica for governmental purposes throughout the world without thepayment to us of any royalty thereon.

This invention relates toan improvedprocess forcarboxymethylatingj'fibrous cellulosic materials and to the novelf'productsj produced there-,-

by. In aparticularly advantageous embodiment it provides 'spinnablecarb'o'xymethylated cotton fibers and a method for their production.

Various types of 'celrboxy'methylated celluloses have beenknowncforzover. thirty :years. The properties and. advantages providedby the presence of carboxymethyl-igroups attached to cellulosic chainsis well-known..---

, 1 Cotton cellulose is unique in that inaddition to being composedofsubstantially pure alphacellulose; in its natural fibrous form, it hasthe properties a staple fiber :must possess in order to be convertedinto yarns and fabrics by the conventional spinning methods andapparatus. These properties .m'e' hereinafter referred to as theproperties of spinnable fibers.

While many processes for the chemical modiper glucose Title 35, U. -S.Code (1952), sec. 266) conducting the carboxymethylation processes whichhas made possible the production of spinnable carboxymethylated staplefibers of cellulose containing up to about 1 carboxymethyl group unit.In addition to their particular advantage of being suitable for mixingwith other staple fibers to form fiber blends having swelling, dyeing,ion-exchange, reactive (for example, for higher'reactivity increase-proofing process 'such as those disclosed in the co-pendingapplication of Daul and Reid, Serial No. 156,032, filed April 14,1950,now Patent No. 2,584,114) and the like properties best suited foraparticular application, the spinnable carboxymethylated cellulose fibersproduced by the process of this invention are more pliable, have abetter hand and feel, a greater flexibility, and a more uniform andgreater tensile strength than that of the carboxymethylcellulosesproduced by any of the processes heretofore known.

As'is described in the patent, cellulose car'- boxymethylated by theprocess of U. S. 2,448,153

' to the extent of 1 carboxymethyl group per 5 to fication of cellulosefibers have been developed,

the bulk of them are not suited for the production of spinnable cottonfibers. For example, while U. S. 2,448,153 discloses a process for theproduction of carboxymethylated celluloses containing 1 carboxymethyl'group per 5 to 40 glucose units in a fibrous form; carboxymethylatedcotton fibers so produced are not spinnable. While the cotton may be sotreated in the form of yarn or threads and-the carboxymethylated yarnsor threads may be woven in the usual manner; they cannot be broken downinto spinnabie cotton fibers dueto their adherence into mats. Similarly,a co-pending application of Daul and Reid, Serial No. 154,202, filedApril 5, 1950, now Patent No. 2,617,707, employing the products of theabove patent as. the preferred starting material, discloses a processfor the production of ferred to carboxymethylated celluloses containingmore than 1 carboxymethyl group per 5 glucose units.

The products of this process are fibrous and water soluble. However,like the former process, the latter is well suited for the production ofyarns, threa s, or textfie, but not spinnable carbcxymethyl-ated cottonfibers.

Modern spinning and weaving practices have demonstrated remarkableadvantages which can be obtained from a blend of two or more kinds ofspinnable staple fibers.

We have discovered an improved method of alkaline solutions.

40 glucose units is insoluble in water and aqueous Since thiscarboxyrnethylation isaccomplished by the action of chloroacetic acid inthe presence of concentrated aqueous solutions of alkali metalhydroxides (two water-soluble reagents); the patent logically teachesthat, upon the attainment of the desired degree of reaction, thecellulosic materials are freed of reactants by mechanical means andwater extraction. The co-pending application reabove teaches that in thepreferred two-step method of producing water-soluble carboxymethylatedcelluloses, the reagents used to carboxymethylate to below 1carboxymethyl group per 5 glucose units (the first step), are removed inthe same manner.

While extraction with an organic solvent rather than with waternecessarily increases the expense of the process and the danger of fire,we have found that in the case of the removal of the reagents employedto carbomethylate a fibrous cellulosic material to the extent of 1carboxymethyl group per 5 to 40 glucose units, the disadvantages aremore than overcome by the advantageous resultS' obtainedr When thestarting material is cotton fiber (in forms such as raw fiber, sliver,

r yarns, etc. that. can be converted to spinnable fiber) theproducts areobtainable as spinnable flexibility. These fibers were capable of beingspun alone, or blended with other spinnable cellulose fibers and thenspun.

The process of the present invention consists of: starting with acellulosic material suitable for carboxymethylation by the processdescribed in U. :5. 2,448,153 in the form of raw'fiber, sliver, roving,yarn, thread, or fabric; carboxymethylating said cellulosic material bythe process of said patent to the extent of 1 carboxymethyl group per to40 glucose units; and removing the carboxymethylat ng reagents from theproduct by mechan cal means and washing with liquid, water-miscible,organic solutions containing from about 1 to 30% water.

The mechanical means for removing the carboxymethylating reagentspreferably comprise a pressing-out or a centrifuging-out of thereagents.

The organic solutions employed to extract the remainingcarboxymethylating reagents from the product can suitably be solutionsof any liquid water-miscible organic compound containing from about 1 to30% water. Liquid water-miscible alkanones and alkanols of not more-than4 carbon atoms are preferred.

A particularly suitable method of conducting the extraction of theremaining carboxymethylation reagents comprises extracting a pluralityof times with such an alkanone or alkanol containing about 5% water andabout 5% of a watermiscible organic acid and then extracting with thealkanone or alkanol containing 5% water.

Acetone and methyl ethyl ketone are preferred alkanones for suchemployment, and. methyl, ethyl, and isopropyl alcohol are preferredalkanols. Acetic and propionic acids are preferred acids.

In the production of fibrous water-soluble carboxymethylated celluloses,the process of the diameter of the fibers. For example, while awater-soluble cotton yarn prepared by the process heretofore known oftenis 20% larger in gauge after carboxymethylation, the same yarncarboxymethylated to the same extent by the present process exhibits noappreciable amount of the undesired change in gauge.

The following examples are presented to illustrate in greater detailcertain features involved in the practice of the present invention.However, as it is apparent that many modifications can suitably be made,the scope of the invention is defined by the claims and is not to beconstrued as being limited to the particular materials and conditionsemployed in the examples.

EXAMPLEI Five skeins of 'mercerized cotton thread were soaked insolutions of 10, 15, 20, 25, and 30% monochloroacetic acid in watercontaining a small amount of wetting agent to aid penetration. Theskeins were centrifugedto about wet pickup, based on the weight of thethread, then soaked in separate portions each of 50% sodium hydroxidesolution. After one-half hour, the skeins were washed in water andneutralized with water containing 5% acetic acid, rewashed, and dried.The tensile strength, elongation, hand or feel, and substitution areshown in-Table 1.

EXAMPLE 2 An identical set of samples was treated as described inExample 1 except that at the end of the reaction time of one-half hour,the samples were centrifuged free of part of the excess alkali and thenwashed several times with 95% ethyl alcohol containing about 5% aceticacid. They were then washed with hot 95% ethyl alcohol. The

4 dried samples were tested in the same way as were TABLE 1 Comparisonof water-washed and alcohol-washed carboxymethylated cotton yams WATER-WASHED 1.

Tenac- Elonga- MCA' Gauge No NaOH ity tion Hand Substf" Percent Lb:Percent 1 "0 50 10. 2 10. 5 2-- 10 50 7,3 11.8 3---" 15 50 6. 3 11. 04"--- 20 50 4. 9 l0. 3 5....-- 25 50 v 4. 2 l0. 6 6..-" 30 2. 5 12. 1

ALOOHOL-WASHED I 1 Samples from Example 1.

' Samples from Example 2. MCA represents monochloroacetic acid.

"Control samples. ""The substitution numb er indicates the averagenumber of carboxymethyl groups pre glucose anhydride residues in thecellulose.

present invention consists of the two-step process of the application ofDaul and Reid, Serial the samples produced by the treatment described inExamplel. The results are shown in Table 1.

The results from Table 1 illustrate the advantages of the organicsolvent wash over the water wash in respect to tensile strength, gauge,and hand.

EXAMPLE 3.

7 I Selected samples from'Examples 1 and 2 were retreated, individually,to make them soluble, as follows: The sample, in skein form, wasimpregnated with 50% monochloroacetic acid in water containing a smallamount of wetting agent to aid penetration. They were then centrifugedto approximately 50% retention of liquid based on the weight of thesample and then soaked in separate portions of 50% sodium hydroxide foronehalf hour. A ratio of approximately 8 parts of the alkaline solutionto one part of the sample, by weight, was used. The samples werecentriiuged to remove most of the excess alkali and then washed withalcohol, neutralized with alcohol containing acetic acid and finallywashed in hot alcohol. Results of tests on these samples and theircorresponding numbers from Examples 1 and 2 are given in Table 2.

TABLE 2 Tensile Yarn fis Number Substi- Sample No.* in Table 1 fituition *Samples 2, 4, and 6 were water-washed after first treatment; 8'10, and 12 were alcohol-Washed.

"The substitution number indicates the average number of carboxymethylgroups per glucose anhydride unit in the cellulose.

EXAMPLE 4 acetic acid.

Washing Tenacity, Treatment Lb.

Water g 0.0392

EXAMPLE '5 Two strips of eighty square cotton cloth were soaked in 30%monochloroacetic acid, centrifuged,, then soaked in 50% sodium hydroxidefor one-half hour. One piece (A) was washed in water containing 5%acetic acid, the other piece (B) was washed in alcohol containing 5%acetic acid, then several times in 80% alcohol.

Washing Tenacit Sample Treatment Lb. y

Substitution '1 x strips broken on Scott tester (0-110 1b.).

EXAMPLE '6 Several yards ofcotton sliver, extracted with acetone toremove waxes, was treated with monochloroacetic acid solution andcentrifuged followed by soaking in a 50% sodium hydroxide solution forminutes. It was washed in alcohol, and neutralized with acetic acid inalcohol.

It was retreated with 55% monochloroacetic acid and 50% sodium hydroxidefor one-half hour, washed with alcohol and acidified with hydrochloricacid in alcohol, then converted to the ammonium salt with ammoniumhydroxide in alcohol.

The sample had a soft hand, was water solu ble, and could be easilycarded.

Another sample washed with water after the first carboxymethylationtreatment was so matted it could not be pulled apart easily.

The carboxymethylated cellulose products, produced according to themethods of the foregoing examples, were easily carded and spun.

Having thus described our invention, we claim:

1. In a process for the production of fibers containing onecarboxymethyl group per each 5 to 40 glucose units by reacting acellulosic material with aqueous monochloroacetic acid and an aqueousalkali metal hydroxide, the improvement which comprises: impregnating acellulosic material composed of spinnable cellulosic fibers with aqueousmonochloroacetic acid; further impregnating the so treated cellulosicmaterial with an aqueous alkali metal hydroxide containing from 20 to50% alkali metal hydroxide; allowing the reaction to proceed until onecarboxymethyl group per 5 to 40 glucose units has been introduced;mechanically removing the aqueous reactants; washing the treatedcellulosic material with a water-miscible organic liquid selected fromthe group consisting of alkanols and alkanones of not more than fourcarbon atoms, said organic liquid containing from 1 to 30% water;recovering a spinnable, strong, pliable, flexible carboxymethylatedfiber; and spinning said carboxymethylated fiber.

2. In a process for the production of fibers containing onecarboxymethyl group per each 10 to 20 glucose units by reacting acellulosic material with aqueous monochloroacetic acid and an aqueousalkali metal hydroxide, the improvement whichcomprises: impregnating acellulosic material composed of spinnable cellulosic fibers with aqueousmonochloroacetic acid; further impregnating the so treated cellulosicmaterial with an aqueous alkali metal hydroxide containing from 20 to50% alkali metal hydroxide; allowing the reaction to proceed until onecarboxymethyl group per 10 to 20 glucose units has been introduced;mechanically removing the aqueous reactants; washing the treatedcellulosic material with a water-miscible organic liquid selected fromthe group consisting of alkanols and alkanones of not more than fourcarbon atoms, said organic liquid containing from 1 to 30% water;recovering a spinnable, strong, pliable, flexible carboxymethylatedfiber; and spinning said carboxymethylated fiber.

GEORGE C. DAUL. JOHN D. REID. ROBERT M. REIN'HARDT.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,448,153 Reid et al Aug. 31, 1948 2,617,707 Daul et a1 Nov.11, 1952 OTHER REFERENCES Matthews Textile Fibers, 5th edition, 1947,page 156.

Textile Research Journal, October 1947, pages 554 to 561.

1. IN A PROCESS FOR THE PRODUCTION OF FIBERS CONTAINING ONECARBOXYMETHYL GROUP PER EACH 5 TO 40 GLUCOSE UNITS BY REACTING ACELLULOSIC MATERIAL WITH AQUEOUS MONOCHLOROACETIC ACID AND AN AQUEOUSALKALI METAL HYDROXIDE, THE IMPROVEMENT WHICH COMPRISES: IMPREGNATING ACELLULOSIC MATERIAL COMPOSED OF SPINNABLE CELLULOSIC FIBERS WITH AQUEOUSMONOCHLOROACETIC ACID; FURTHER IMPREGNATING THE SO TREATED CELLULOSICMATERIAL WITH AN AQUEOUS ALKALI METAL HYDROXIDE CONTAINING FROM 20 TO50% ALKALI METAL HYDROXIDE; ALLOWING THE REACTION TO PROCEED UNTIL ONECARBOXYMETHYL GROUP PER 5 TO 40 GLUCOSE UNITS HAS BEEN INTRODUCED;MECHANICALLY REMOVING THE AQUEOUS REACTANTS; WASHING THE TREATEDCELLULOSIC MATERIAL WITH A WATER-MISCIBLE ORGANIC LIQUID SELECTED FROMTHE GROUP CONSISTING OF ALKANOLS AND ALKANONES OF NOT MORE THAN FOURCARBON ATOMS, SAID ORGANIC LIQUID CONTAINING FROM 1 TO 30% WATER;RECOVERING A SPINNABLE, STRONG, PLIABLE, FLEXIBLE CARBOXYMETHYLATEDFIBER; AND SPINNING SAID CARBOXYMETHYLATED FIBER.